AQA A Level Chemistry

Revision Notes

2.1.3 Trends of Period 3 Elements: First Ionisation Energy

Trend: First Ionisation Energy

  • The first ionisation energy (IE1) is the energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous ions
    • Eg. the first ionisation energy of Na is:

Na (g) → Na+ (g) + e

IE1 Values of the Period 3 Elements

The Periodic Table - Table_Variation in First Ionisation Energy, downloadable AS & A Level Chemistry revision notes

  • There is a general increase in IE1 across a period
    • The nuclear charge increases
    • The atomic radius decreases
    • There are stronger attractive forces between the nucleus and outer electrons
    • It therefore gets harder to remove any electrons
  • Small ‘dips’ are observed between Mg – Al and P – S

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